macOS 27 Golden Gate broke your Microsoft apps: every known issue (September 2026).

OneDrive can't find your "OneDrive (2026-09-13 …)" folder after upgrading to macOS 27.

Reported on Microsoft Q&A from September 19, 2026, five days after Golden Gate shipped. After the upgrade OneDrive stops syncing and shows a dialog saying it couldn't find your "OneDrive (2026-09-13 05:36:04 +0000)" folder, with Try Again and Stop Sync buttons that do nothing useful. The menu bar icon offers only Close OneDrive and Stop Sync, and the folder it names, timestamp and all, does not exist. Your real OneDrive folder is still there, which is what makes the dialog so confusing.

Cause

The upgrade left OneDrive's File Provider registration pointing at a sync location that no longer exists. On current macOS, OneDrive syncs through Apple's File Provider framework and keeps its actual folder under ~/Library/CloudStorage/, with the OneDrive folder you see in Finder acting as a pointer to it.

Every report in the thread involves the Mac App Store build of OneDrive (bundle ID com.microsoft.OneDrive-mac); one user hit it on an M1 iMac but not on an M3 MacBook Air running the same App Store build. Two users resolved it by replacing the App Store build with Microsoft's standalone download. Reinstalling the App Store build did not help, and OneDrive's own reset script returned "Operation not permitted" errors on the container folders and did not clear it either.

The fix that has worked

1. Confirm your files are safe before touching anything. Sign in to OneDrive on the web (onedrive.com for personal accounts, office.com for work accounts) and check that recent files are there. Then in Finder press Cmd+Shift+G, go to ~/Library/CloudStorage, and copy anything in the OneDrive folders that changed recently to a folder outside OneDrive, ideally an external drive. Microsoft's reset guidance warns that a reset can discard local changes that never uploaded.
2. Find out which OneDrive you have. In Terminal run /usr/libexec/PlistBuddy -c 'Print CFBundleIdentifier' /Applications/OneDrive.app/Contents/Info.plist. A result of com.microsoft.OneDrive-mac is the App Store build; com.microsoft.OneDrive is the standalone build.
3. Quit OneDrive. Use the menu bar icon; if that does nothing, force quit it from Activity Monitor. Then drag OneDrive from Applications to the Trash and empty the Trash. Only one OneDrive build can be installed at a time, and the two cannot sync the same content.
4. Install the standalone build from Microsoft, not the App Store, via Microsoft's reinstall OneDrive page. Sign in.
5. When setup asks where to put your files, choose the existing OneDrive location so unchanged files are not downloaded again. Do not create another folder, and do not delete either timestamped folder under CloudStorage until sync has finished and you have confirmed everything on the web.
6. If the standalone build shows the same dialog, run the reset script bundled with it: Control-click OneDrive in Applications, choose Show Package Contents, open Contents, then Resources, and double-click ResetOneDriveAppStandalone.command (the App Store build ships ResetOneDriveApp.command). Open OneDrive and sign in again.

The reports so far are personal accounts, but the File Provider mechanism is the same for work accounts, so treat a work Mac that shows this dialog the same way. Copy first, swap builds second, delete nothing until sync is green and verified online.

Your Intel Mac cannot install Golden Gate, and Microsoft's support window is moving.

Golden Gate dropped every Intel Mac; Apple has said Tahoe 26 is the final macOS for them. Microsoft supports Microsoft 365 for Mac, Office 2024, and Office 2021 on the three most recent major macOS versions and removes the oldest when a new one goes generally available. Golden Gate's release therefore moves the window to 27, 26, and 15, and pushes Sonoma 14 out.

Last year the cut landed in the same month Tahoe shipped: the September 2025 build, 16.101, was the last to support Ventura. As of September 23, 2026, Microsoft's lifecycle page still carries the 2025 wording, so the exact last-Sonoma build is not published yet.

Intune is moving in step: the Company Portal and the MDM agent support macOS 15 and later shortly after the macOS 27 release, so a Sonoma Mac already enrolled stays enrolled, but a new one cannot enroll.

What to do with each Mac

1. Inventory first. On each Mac, Apple menu, then About This Mac: note the chip (Apple silicon or Intel) and the macOS version. A ten-person office usually has one or two Macs it has forgotten about.
2. Intel Macs: get them to Tahoe 26 now if they are not there already, and turn on automatic updates. Under the current policy that buys Microsoft 365 updates through fall 2028, which is a reasonable replacement horizon.
3. Sonoma Macs that can run Sequoia or Tahoe: upgrade before the fall Office update drops Sonoma. Sonoma Macs that cannot go higher lose Office security updates this fall and cannot be newly enrolled in Intune, so plan their replacement within the next twelve months.
4. Anything on Ventura or older is already off updates. If Office on one of these Macs opens files but refuses to edit or save, that is the July 13 licensing change, not a bug, and no reinstall fixes it. Use Microsoft 365 on the web until the Mac is replaced.
5. Do not upgrade your only Mac to Golden Gate on day one. University IT departments managing thousands of Macs are telling staff to wait for the first point releases. Before any upgrade, run Help, then Check for Updates in an Office app, and confirm OneDrive has finished syncing: a green icon does not mean every file is stored locally.

October 1: legacy Outlook for Mac and Apple Mail start losing Exchange Online.

Microsoft starts blocking Exchange Web Services (EWS) requests to Exchange Online on October 1, 2026, in a phased, admin-controllable rollout that ends with a complete shutdown in 2027. Two Mac mail clients depend on EWS. Legacy Outlook for Mac connects through it and stops working with Exchange Online mailboxes beginning October 2026.

Apple Mail on the Mac also uses EWS for Exchange accounts; Apple is working with Microsoft to move Mail, Calendar, Contacts, Notes, and Reminders to Microsoft Graph in a future update to macOS 27, which means the fix, when it ships, lands on Golden Gate and not on the Tahoe Macs that cannot upgrade. Universities that manage thousands of Macs are already warning staff that Apple's update may not arrive before October 1.

Get ahead of it this week

1. Outlook for Mac: open Outlook and look at the Outlook menu. If Legacy Outlook is checked, uncheck it to move to the current client. If the toggle is not there, choose Help, then Check for Updates, and install the latest build.
2. Apple Mail with a Microsoft 365 account: if the Mac can run Golden Gate, upgrade and install every macOS 27 point update as it arrives; the Graph-based Mail update ships there. If it cannot (Intel), move the account to Outlook for Mac now, or use Outlook on the web.
3. iPhone and iPad Mail are widely reported to have already moved off EWS. Keep iOS current and re-add the account if it asks you to sign in again.
4. Admins: the October rollout is phased and controllable per tenant. If Apple's update is not out when your users break, you can keep EWS enabled for the tenant for a few more months, but 2027 is the hard stop. Check the third-party tools that touch mailboxes too: CRM sync, backup, and multifunction printers that scan to email are the usual EWS holdouts.

Word, Excel, PowerPoint, or Outlook crash or will not open after the upgrade.

Nine days in, there is no Microsoft-confirmed Golden Gate incident for the Office apps, and the reports so far follow the pattern of every macOS launch: apps that were out of date before the upgrade, or helper components the upgrade relocated. Microsoft ships macOS compatibility fixes through app updates and does not support its apps on beta or preview builds, so the current builds matter more than anything else on this list.

The ladder, in order

1. Update Office first. Open any Office app that still works, choose Help, then Check for Updates, and install everything Microsoft AutoUpdate offers. As of this update the current Microsoft 365 for Mac build is 16.112.
2. Update macOS. System Settings, General, Software Update. Install the latest 27.x point release; the first point releases after a major version are where launch bugs get fixed.
3. Check Relocated Items. A major upgrade moves incompatible files into a Relocated Items folder (an alias appears on the Desktop). If Microsoft helper items landed there, reinstall the affected app.
4. Outlook only: hold Shift while launching to start it in a reduced state and rule out a corrupt window layout.
5. Reset preferences. Quit the app, press Cmd+Shift+G in Finder, go to ~/Library/Preferences, and move the matching com.microsoft.* files to your Desktop. Relaunch; macOS rebuilds fresh ones.
6. Clean reinstall. Delete the Office apps from Applications, then in ~/Library/Group Containers remove the folders that begin with UBF8T346G9, empty the Trash, restart, and reinstall from office.com. Warning: this signs you out of Office on this Mac and clears local caches and settings.
7. Isolate the profile. Create a new macOS user account in System Settings, Users & Groups, and launch the app there. If it runs clean, the problem lives in your user profile, not in Office or Golden Gate.

Teams is supported on 27, 26, and 15. If the location permission loop (Microsoft incident TM1315837) comes back after the upgrade, the toggle-off-and-on workaround in our Tahoe guide still applies.

Quick answers.

Does Microsoft 365 work on macOS 27 Golden Gate?

Yes. The current Microsoft 365 for Mac apps support Golden Gate under Microsoft's three-version policy, which now covers 27, 26, and 15. Update the apps before you upgrade the OS. The one confirmed breakage so far is the App Store build of OneDrive losing its sync folder; the standalone build fixes it.

Why does OneDrive say it can't find my OneDrive folder after upgrading to macOS 27?

The upgrade left OneDrive's File Provider registration pointing at a timestamped sync location that no longer exists. Back up any unsynced files, remove the App Store build, install the standalone OneDrive from Microsoft, and choose your existing folder during setup.

Can an Intel Mac upgrade to macOS 27 Golden Gate?

No. Golden Gate runs on Apple silicon only, and Tahoe 26 is the last release for Intel Macs. Under Microsoft's policy an Intel Mac on Tahoe keeps receiving Microsoft 365 updates until macOS 29 ships, expected in fall 2028.

Will Apple Mail stop working with Microsoft 365 on October 1, 2026?

It can. Microsoft begins blocking EWS on October 1 in a phased rollout, and Apple Mail on the Mac still uses EWS for Exchange accounts. Apple's Graph-based update is planned for macOS 27. Until it ships, use Outlook for Mac or Outlook on the web, or have your admin keep EWS enabled temporarily.

Is legacy Outlook for Mac still supported?

No. It connects through EWS and stops working with Exchange Online mailboxes beginning October 2026. Uncheck Legacy Outlook in the Outlook menu to move to the current client.

When it is not your Mac.

Three honest exclusions. If the same account fails on every device, it is a Microsoft 365 service or account issue, not the Mac, so check whether Microsoft 365 is down before touching the machine. If mail stops on or after October 1 and the client is legacy Outlook or Apple Mail, the cause is the EWS retirement above, and the fix is a client change, not a reinstall. And failing hardware, a dying SSD or bad RAM, can masquerade as app crashes; frequent crashes across non-Microsoft apps too point there.

Sources.

• Microsoft Q&A: OneDrive folder not found after upgrading to macOS 27, September 19 to 23, 2026.
• Reinstall OneDrive, support.microsoft.com, accessed September 23, 2026.
• Upgrade macOS to continue receiving Microsoft 365 and Office for Mac updates, support.microsoft.com, page last updated June 2026, accessed September 23, 2026.
• Certificate update for Microsoft 365 apps on managed macOS and iOS devices, learn.microsoft.com, May 2026.
• Update Microsoft 365 or Office on your macOS or iOS device, support.microsoft.com, September 2026.
• Retirement of Exchange Web Services in Exchange Online, Microsoft Tech Community, updated September 2026.
• Microsoft Exchange Web Services ending October 1, 2026, William & Mary IT.
• Microsoft retires EWS API on October 1 and Wait to upgrade to macOS Golden Gate, CU Boulder OIT, September 2026.
• The end of EWS in Mail, Michael Tsai, August 20, 2026 (Apple's Graph migration planned for macOS 27).
• Microsoft Intune, in development, learn.microsoft.com, September 2026, and Message Center MC1403402 / MC1454370.
• macOS 27 Golden Gate compatibility, MacHow2, September 2026.
• macOS release history, Wikipedia, accessed September 23, 2026 (27.0 released September 14, 2026).